Cities, Resilience, Security and Risk, Seismic, Structural
In areas like San Francisco, earthquakes are a very real threat to the built environment. Resilience-based earthquake design (REDi) is a tiered rating procedure that communicates seismic risks to building owners and stakeholders. REDi also encourages beyond-the-code design to protect their assets following an earthquake.
This cross-regional follow-up investment aimed to ensure that REDi can be applied to existing buildings in Europe too. We also made minor adjustments to the loss assessment for different localities.
Eurocode and the Turkish Earthquake Code (2007) already include performance-based design and evaluation features, which provide only ‘life safety’ for building occupants in an earthquake.
In Turkey, there is a lack of awareness about the business interruption and financial loss that follows an earthquake. Additionally, local clients are generally unfamiliar with the implications of performance limits. Promoting this rating system with its beyond-the-code features will drastically improve understanding of earthquake code and application.
This project proposed:
- Additional regional requirements for the original REDi (i.e. instead of ASCE 7-10, code minimum requirements now must be adopted from Eurocode and the Turkish Earthquake Code)
- Evaluated an existing mid-rise commercial building
- Rated the building according to REDi (see IiA 7943)
- Carried out loss assessment studies using FEMA P-58 and PACT
- Defined major causes of delays and financial losses
- Proposed several enhancements to the design to achieve silver or gold ratings
- Made engineering judgments and adjustments on FEMA P-58 results to be consistentwith local conditions (for example, impeding factors and downtime might be different).
- Estimating only downtime for repair would not be sufficient for a business interruption calculation
- REDi estimates downtime for delays, disruptions, repairs and permits
- Strengthening a low-rise building by introducing a new shear wall can prevent
- Repairing non-structural components may take longer than repairing structural elements
- Strengthening an existing low-rise r.c. building with
- new shear walls would not eliminate all risks on non-structural components
- Simple improvements to acceleration-sensitive non-structural components can significantly reduce the downtime
- Inability to obtain financing following an earthquake can significantly affect total downtime — this varies from country to country
- The REDi procedure can easily be adapted for Europe.
The framework developed by the research team helped considerably in proposing regional requirements to the original REDi codes — in evaluating existing mid-rise commercial buildings and in rating them according to REDi.
The research team carried out loss assessment studies, defining major causes of time delays and financial losses. This work has enhanced the proposed design so it will achieve silver or gold ratings. Finally, we were able to make engineering judgements and adjustments to FEMA P-58 results so it is consistent in each
While minor modifications to our system may be needed, REDi procedure can also be used for the review of existing buildings/facilities in other countries, including in Europe. This will give clients a better understanding of the business interruption risks occur following earthquakes due to non-structural components.
For the last decade, performance-based design (PBD) procedures have helped engineers to validate their preliminary designs with target performance levels for factors such as life safety and immediate occupancy.
On the other hand, it has not been so clear to building owners / stakeholders how these performance levels affect the interruption to their business following an earthquake. Resilience-based Earthquake Design (REDi) can communicate information like this to facility owners.
Using REDi, Arup can help clients understand earthquake risk in terms of downtime. They can then easily estimate potential business interruption losses.
The procedure is also an effective way to evaluate existing essential facilities. Arup can easily demonstrate mitigation alternatives, and their downtime consequences to clients and stakeholders. The following figure illustrates how repair time is shortened in an example building as we introduce improvements one at a time.